Insulators are devices which are used in
Electrical Supply Networks to supply and separate conductors at high
voltage transmission lines. All insulators have dual functions:
providing mechanical support for the conductors and also preventing
passage of electrical current to ground.

Although, insulators make a few percentage
of the total cost of overhead line projects; they have a great and
inevitable role in reliability of the lines, and safety of people's
daily life .

Since 1950s, use of toughened glass
insulators increased on all high voltage overhead lines, for AC up
to 800kV and for DC up to 600kV. The reliability of high quality
toughened glass insulators and easy maintenance are of key factors
to its success.

Why toughened
glass?

Annealed glass insulators are susceptible
to micro cracks, voids and inclusions especially on their surface.
Under mechanical (Impact or tension) and electrical loads, these
might cause crack initiation and propagation leading to complete
shattering of the insulator.

For overcoming these deficiencies "Toughening" process was
introduced in late 1940s which improved the mechanical
characteristics of molded glass dielectric shells without affecting
their already superior electrical properties. Since then toughened
glass insulators have been increasingly used on high voltage
overhead lines, worldwide. PARS MAGHAREH Company uses "Toughening"
process in its manufacturing line.